This invention relates to a method of controlling the operation of a power plant, and apparatus for performing the method. More particularly, it relates to a method of operating a power plant including a gas turbine power generating unit, a gas turbine waste heat recovery boiler whose heat source is the exhaust gas of the gas turbine, and a back-up boiler which backs up the waste heat recovery boiler, and also to apparatus for performing the method.
In a power plant including a gas turbine power generating unit and a main boiler whose heat source is the waste heat of the gas turbine, when the fluctuation of a heat load (for example, steam turbine) driven by steam produced by the main boiler is great, the quantity of steam becomes insufficient with only the steam produced by the main boiler. In order to compensate for the insufficient quantity of vaporization of the main boiler, a back-up boiler is usually provided. The back-up boiler is operated only when the quantity of vaporization of the main boiler is insufficient, whereas it is stopped when the heat load can be satisfactorily driven with only the quantity of producing steam of the main boiler.
A problem in the power plant of the type described above is that when the heat load of the power plant has increased suddenly, the back-up boiler normally held in the shutdown state cannot be rapidly started, so the supply of energy to the heat load becomes insufficient temporarily. As one expedient for solving the problem, it is thought to normally operate the back-up boiler. This measure, however, is unfavorable in being very uneconomical and in lowering the thermal efficiency of the power plant.